Dell C1765NF MFP Laser Printer - Manual (Page 216)

214 Loading Print Media
8 Adjust the width guides until they rest lightly against the edges of the stack of print media.
9 Slide the length guide towards the printer until it touches the print media.
NOTE: Depending on the size of print media, first slide the MPF extension backward until it stops, and then pinch the
length guide and slide it backward until it touches print media.